Struct gtk4::LayoutManager

#[repr(transparent)]
pub struct LayoutManager { /* private fields */ }

Layout managers are delegate classes that handle the preferred size and the allocation of a widget.

You typically subclass LayoutManager if you want to implement a layout policy for the children of a widget, or if you want to determine the size of a widget depending on its contents.

Each Widget can only have a LayoutManager instance associated to it at any given time; it is possible, though, to replace the layout manager instance using WidgetExt::set_layout_manager().

Layout properties

A layout manager can expose properties for controlling the layout of each child, by creating an object type derived from LayoutChild and installing the properties on it as normal GObject properties.

Each LayoutChild instance storing the layout properties for a specific child is created through the LayoutManagerExt::layout_child() method; a LayoutManager controls the creation of its LayoutChild instances by overriding the GtkLayoutManagerClass.create_layout_child() virtual function. The typical implementation should look like:

⚠️ The following code is in c ⚠️

static GtkLayoutChild *
create_layout_child (GtkLayoutManager *manager,
                     GtkWidget        *container,
                     GtkWidget        *child)
{
  return g_object_new (your_layout_child_get_type (),
                       "layout-manager", manager,
                       "child-widget", child,
                       NULL);
}

The property::LayoutChild::layout-manager and property::LayoutChild::child-widget properties on the newly created LayoutChild instance are mandatory. The LayoutManager will cache the newly created LayoutChild instance until the widget is removed from its parent, or the parent removes the layout manager.

Each LayoutManager instance creating a LayoutChild should use LayoutManagerExt::layout_child() every time it needs to query the layout properties; each LayoutChild instance should call LayoutManagerExt::layout_changed() every time a property is updated, in order to queue a new size measuring and allocation.

This is an Abstract Base Class, you cannot instantiate it.

Implements

LayoutManagerExt, glib::ObjectExt

Implementations

impl LayoutManager

pub const NONE: Option<&'static LayoutManager> = None

Trait Implementations

impl Clone for LayoutManager

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LayoutManager

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for LayoutManager

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for LayoutManager

fn hash<H>(&self, state: &mut H)where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: LayoutManagerImpl> IsSubclassable<T> for LayoutManager

fn class_init(class: &mut Class<Self>)

Override the virtual methods of this class for the given subclass and do other class initialization.

fn instance_init(instance: &mut InitializingObject<T>)

Instance specific initialization.

impl Ord for LayoutManager

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl ParentClassIs for LayoutManager

type Parent = Object

impl<OT: ObjectType> PartialEq<OT> for LayoutManager

fn eq(&self, other: &OT) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<OT: ObjectType> PartialOrd<OT> for LayoutManager

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for LayoutManager

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for LayoutManager

impl IsA<LayoutManager> for BinLayout

impl IsA<LayoutManager> for BoxLayout

impl IsA<LayoutManager> for CenterLayout

impl IsA<LayoutManager> for ConstraintLayout

impl IsA<LayoutManager> for FixedLayout

impl IsA<LayoutManager> for GridLayout

impl IsA<LayoutManager> for OverlayLayout